Just to demonstrate that it is all about choices and preferences, and that there are no "right" answers, I am going to disagree with both Charles and David.
I have both the 10" Tormek as well as a 8" dry grinder with a 48 grit white Norton wheel. If one simply compared the speed with which the dry grinder removed steel, the Tormek is not in the running. The Tormek is quicker than most realise when the wheel is clean and used at the lower 220 grit. However, it is still going to hollow grind the steel from a 2" O1 plane blade in about 3 minutes versus the 1 minute for the dry grinder.
The large Tormek also creates a shallower hollow, actually quite shallow - it is possible to hone away the hollow quite quickly. The up side of this is that one can use it on laminated steel without removing the backing layer. One needs to refresh the hollow after about 4 or 5 honings, but this is quick thanks to the angle setter, and the only steel removed is inside the hollow, not from the length of the blade.
So far the dry grinder seems to be the winner. However, there is another factor, and this is where the Tortoise overtakes the Hare.
The Tormek, being a wet grinder, runs very cool. You can grind to the very edge of the blade without fear of burning the thin steel there. You can also hollow grind laminated Japanese blades without fear of affecting the hard steel layer. By grinding to the edge, it take one or two passes on a 5000 or 6000 grit waterstone to create a micro bevel. It takes about 5 passes on a 13000 waterstone to complete the polishing stage. And you are ready to go. This process takes about 30 seconds.
On a dry grinder one would have to stop about 2mm from the edge to avoid heat damage. At this point you need to begin with a 1000 grit waterstone to create a larger micro bevel (not sure it it is a "micro" bevel any longer), and I'd estimate that this takes about 2-3 minutes. And then you still need to move to the 6000 and 13000 stones, each of which takes many more passes than on the primary hollow from the Tormek as the primary bevel is wider.
Furthermore, the hollow grind on the Tormek is controlled by the guide, and it ends up being very even in width. The hollow on the dry grinder tends to be made freehand. I am quite decent at this, but still end up with an edge that needs to be straightened on the 1000. This adds to the time in preparing the final working edge. Remember, it is the time in achieving a working edge that determines the speed of the machines, and in this manner you will find that the Tormek is the faster machine overall.
Lastly, a further advantage of a clean hollow is that it makes it easier to freehand if, as I do, one uses the hollow as a jig. Grind the hollow primary at the angle desired, and freehand directly on this. Quick and easy. But not for everyone.
Regards from Perth
Derek